Debt Stability Under Entitlement Spending

Abstract

Economists have traditionally used a simple rule that restricts primary deficits to less than a threshold given by the interest rate growth rate differential and existing debt level to judge fiscal sustainability. This rule derives from a single period application of the government’s budget constraint. It does not allow for the predictable dynamic effects of spending liabilities, such as entitlement spending. In this paper, we derive the equivalent dynamic rule for this case. It still depends on the interest growth rate differential, but now includes a restriction on spending growth in relation to income growth. Several new results emerge. Debt remains stable; but the rate of convergence to stability varies with different parameters. And the growth in spending has to be less than a damping factor that controls convergence. This puts a limit on spending growth. To penalize the use of unpopular taxes further limits debt and the incentive to use debt finance.